power: supply: charger-manager: replace deprecated strncpy with strscpy

strncpy() is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.

We expect cm->psy_name_buf to be NUL-terminated based on its usage with
format strings:
1522: cm->charger_psy_desc.name = cm->psy_name_buf;
...
1587: dev_err(&pdev->dev, "Cannot register charger-manager with name \"%s\"\n",
1587:   cm->charger_psy_desc.name);

Moreover, NUL-padding is not required as `cm` is already zero-allocated
and thus any future NUL-byte assignments (like what strncpy() will do)
are redundant:
1437: cm = devm_kzalloc(&pdev->dev, sizeof(*cm), GFP_KERNEL);

Considering the above, a suitable replacement is `strscpy` [2] due to
the fact that it guarantees NUL-termination on the destination buffer
without unnecessarily NUL-padding.

Let's also opt for the more idiomatic strscpy() usage of:
strscpy(dest, src, sizeof(dest)).

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
Link: https://github.com/KSPP/linux/issues/90


Cc: linux-hardening@vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt@google.com>
Link: https://lore.kernel.org/r/20231020-strncpy-drivers-power-supply-charger-manager-c-v1-1-698f73bcad2a@google.com


Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>